Vaillant boiler issues F28 on ecotec 430 not the normal culprit

[Navi Bhander]

Hi there,

I’m hoping someone can help the last 9 months of intermittent issues we’re having.

We live in a large house which is heated by 2 Vaillant ecotec plus 430 system boilers. They’re wired up together so will work at the same time.

They are used to supply underfloor heating downstairs, 300l megaflo and radiators upstairs.

There are valves controlling the flow to each one and one large pump that circulates the water.

The house is controlled by Honeywell’s evohome system, 2 controllers to be precise.

The issue we’re having is sometimes the boilers don’t fire up. F28 fault code. The gas company over a period of months came and checked, they were adamant there wasn’t a gas issue but the pressure was on the low side of normal, 16-19mb and fluctuated.

After months they upgraded the gas pipe from the main road to the house to a 63mm pipe and the gas pressure is now 20mb.

The issue has always been intermittent from Day 1. Sometimes daily sometimes once a week. There is a G6 gas meter and a 28mm pipe from there to the boiler which splits in s t junction and goes to each boiler right under them, in 15mm.

I’ve still got the problem!! Can anyone else help.

One thing I have noticed is when the boiler switch on the the flame symbol comes up with the boiler output gauge display for a few seconds, switches off and then comes back. I presume this is a failed ignition attempt? It seems to do this regularly.

As I have 2 boilers that fire up at the same time and they’re both under 2 years of age I’ve presumed they both can’t be faulty.

Can someone please help as getting up in the morning to run downstairs to reset these things is annoying beyond words now!

 

[chris watkins]

Brilliant explanation Chris. No offence meant by the college tutors thing. Mine were brilliant and were very much up to speed, sorry the op seemed to imply his weren’t quite so

Absolutely no offence taken Riley!!
I know all about the poor levels of knowledge & experience out there in FE land. When you have seen store man or newly qualified Plumbers stuck in front of a class & asked to deliver this very technical subject it is no wonder there are so many poor people out there.
It was just to point out (& as you found) there are still a few of us who try very hard to stay on the cutting edge, mind you what is all this malarkey about controlling a boiler via your hand held telephone....?

 

[Riley]

Well it’s just a gimmick. The whole boiker plus thing is too

 

[pepsidog]

Just done quick pipesize calc and for 8 metres gas pipe, 8 bends and 1 tee on 60kw nett boilers smallest gas pipesize is 35mm. On your picture you show 28mm but then 15mm + couple of bends to boiler . Pressure drop through this would be huge. For these size boilers should be 35mm to as close to gas inlet as possible then 35mm to 22mm reducer then 22mm to 1/2 conex to boiler.
You need gas safe engineer to work out properly. You mention original gas pressure were 16mb. Not sure whether this is at meter or appliance but too low and no gas safe engineer would commission at these pressures as appliance would be classed as “at risk”.
Looking at picture it looks like a diy install, cables all over place.
Best to get Vaillant out to do properly.

 

[Aire]

16mb is not too low and i would commission a boiler at this pressure. All boilers sold in the UK have to work properly at pressures down to 14mb. The only thing you have to maintain is the 1mb drop accross the installation pipe work. And yes his gas pipes are probably undersized but we dont know where his metre is in relation to the boilers so we can't know for sure. he's also getting the same issue when only one boiler is working, in which case the 28mm supply would be adequate.

 

[Abuali]

The only thing you have to maintain is the 1mb drop accross the installation pipe work..

How would you achieve or confirm that 1 mbar drop?

Would you add a test point at the end of pipework just before the boiler isolation valve?

Sorry as i had not seen any engineer install a test point in there, apart from commercial (for tightness testing mainly)

As most of posts in many forums will say the P1 at the gas valve is the test point although gas safe Register Technical Bulletins (tec bulletin 129 published 16 February 2016) acknowledges a possible drop of 0.5-2.5 mbar at the inlet side of the appliance gas control valve.

The Gas supplier must provide a minimum of 19 mbar at the outlet of EcV at peak flow conditions. The pressure drop across primary meter can be up to 4 mbar, leave us with 15 mbar take drop of 1 mbar for pipework then its 14 mbar, and average of 1.5 mbar drop through the appliance pipework and then you end up with a reading of 12.5 mbar at Inlet to boiler gas valve.

I think, and please do correct me if am wrong on this: the key issue in this whether the pressure drop affects the safe operation of the appliance or contibutes to a fault condition then GIUSP should be followed and a Gas rate will confirm a satisfactory operation (GSIUR 26.9(c)) Esp with the zero govenor or Air/gas ratio valves where burner pressure measurement is not appropriate

 

[Riley]

The maths will tell you if your pipework to appliance is below 1mbar drop. What the appliance will work at is inconsequential as this prerequisite must be met in the first instance.

 

[Harvest Fields]

Why are we still talking about this in an open forum? I thought the OP had an engineer that was sorting him out?

 

[Riley]

Yes it has strayed rather

 

[gmartine]

Could this scenario some how cause the boiler has supply issue as it’s just ignites and then switches off due to the demand not being required anymore?

I’m mechanically competent and used to restore classic cars. If you start a car but switch it off without it fully turning over it sometimes results in it flooding and difficult to start the next time. In very layman terms could this happen with gas?

How are you getting on, anything to update?